Method of preparing synthetic rubber



Patented Sept. 11, 1945 STATES PATT orrlcg METHOD or PREPARING s nan Charles F. Fryllng, 11, Ohio,

or, by

mesne assignments, to The B. F. Goodrich Company, on, Ohio, a corporation of New York No Drawing. Application June 27, 1941, V Serial No. 400,093

This invention relates to the preparation of synthetic rubber and particularly to rapid preparation of synthetic rubber-like materials from mixtures of butadiene-1,3 hydrocarbons.

It has previously been known that butadiene and isoprene may be copolymerlzed in the form of an aqueous emulsion. In previous processes, however, the polymerization has required a long time" and the products have been weal: and inextensibler it is the principal object of this invention to prepare copolymers of butadiene-LS hydrocarbons by a polymerization process which ordinarily requires not over three days andproduces extensible polymers exhibiting sumclent tensile strength to make them useful as a replacement for natural rubber.

By the method of this invention, at least two butadiene-L3 hydrocarbons are copolymerized in an aqueous emulsion in the presence oi an alphamethylene nitrile. The invention further con templates in the preferred modification, the use of a water-soluble soap derived from a fatty acid containing between and 20 carbon atoms per molecule as the emulsifying agent, and conducting the polymerization in the presence of a compound containing a heavy metal as will hereafter be described.

By the term butadiene-LS hydrocarbon" is meant butadiene-Ld, commonly called butadlene and homologues of butadlene-L3 which enter into to the --CEN group, such as acrylonitrlle, alpha- I methacrylonitrlle, alpha-ethacrylonitrile, alphamethoxy-methacrylonitrlle, alpha-chlormethacrylonltrlle, etc. The preferred synthetic rubbers of this invention are prepared in the presence of from about 2 to 10% by weight based on the butadlene hydrocarbons of an alpha-methylene nitrile, particularly acrylonitrlle.

It is preferred to conduct the polymerization in the presence of between 5 and by weight based on the butadiene hydrocarbons of an emulslfylng agent consisting of a water-soluble soap derived from a fatty acid containing between 10 and carbon atoms per molecule such as lauric acid, myrlstic acid, palmitic acid, oleic acid, or stearic acid. Any water-soluble soap such as 5 those derived from the fatty acid by reaction with sodium or potassium hydroxide may be emplayed. It is in general desirable to conduct the polymerization in the presence of free fatty acid; 1. e. in the presence of fatty acid which is only 10 85 or 90% neutralized, although polymerlzatlons may be conducted in the presence of completely neutralized soap or even in the presence of free alkali. The polymerization may also be efiected under acid conditions, in which case the salts of 5 organic bases containing long carbon chains such as the hydrochloride of diethylamlnoethyloleylamide, trimethylcetylammon'ium 'methyl sulfate,

the hydrochloride of oleylamidoethyldimethylamine, the hydrochloride of the diethylamino- 20 ethoxyanilide of oleic acid, etc., may be employed,

or under acid alkaline, or neutral'conditlcns in the presence of emulsifying agents such as hymolal sulfates and aryl sulionates such as sodium lauryl sulfate, sodium isobutyl naphthalene sules fonate, etc.

The polymerization is preferably conducted in the presence of a small amount of a heavy metal catalyst. The heavy metal catalyst may be added to the emulsion in the form of less than .1% based on the weight of the monomers of simple lonizable heavy metal salt such as cobalt chloride, nickel sulfate, mercuric chloride, etc, as disclosed in the copending application of William D. Stewart, Serial No. 379,712, filed February is, 1941 or in the form of a redox system comprising a heavy metal and a material such as sodium pyrophosphate, levulinic acid, glycine, cystlne, beta-mercaptoethanol, quebrachitol, ox-blle, or cholesterol, as disclosed in the copending applications of William D. Stewart, Serial NOS. 379,713 to 379,717,

filed February 14, 1941.

The polymerlzationmay be efiected by various initiators of polymerization such as per -compounds including hydrogen peroxide, benzoyl peroxide, ammonium persulfate, potassium persulfate, and other peroxides and persalts such as persulfates, perborates, percarbonates, and the like, as well as other types of initiators such as dlazoaminobenzene, dipotassium diazomethane disul-' 0 fonate, and triphenylmethylazobenzene. Sulfurcontainlng organic compounds, herein called modifiers, which increase the plasticity and solubility of the polymers such as diallwl dixanthogens, the higher tetraalkyl thiuram mono-, (11-,

and polysulfides, 2-mercaptoalkylthiazoles, and

2 bls-alkylthiazyl-2 disulfldes are also preferably present in the emulsion during the polymerization.

As a specific example of the method by which the three-component copolymers of this invention may be prepared, 50 parts by weight of butadiene, 50 parts of isoprene, 3 parts of acrylonitriie, and 0.35 part of hydrogen peroxide as an initiator were agitated at 30 C. in about 250 parts or a 2% aqueous solution of myristic acid which had been 85% neutralized with sodium hydroxide. After 65 hours, a latex-like dispersion was obtained which, when stabilized and coagulated, yielded 93 parts of a. three-component copolymer of butadiene, isoprene and acrylonitrile. When the experiment was repeated employing a two-component system containing 50 parts of butadiene and 50 parts of isoprene, no copolymer was formed after 65 hours at 30 C. and an additional 24 hours at 35 C.

In another experiment, 50 parts of butadiene, 50 parts of isoprene, 3 parts of acrylonitrile, 0.35 part of hydrogen peroxide, 0.37 part of sodium ferripyrophosphate as an activator, and .6 part of diisopropyl dixanthogen as a modifier were agitated at 30 C. .in about 250 parts of a 5% aqueous solution of myristic acid which had been 85% neutralized with sodium hydroxide. A latex-like dispersion was obtained which, upon stabilization with phenyl-beta-naphthylamine and coagulation with a saturated sodium chloride solution, yielded 94 parts of a three-component copolymer of butadiene, isoprene, and acrylonitrile. When tested in a tire tread recipe, the copolymer exhibited a. tensile strength of 2600 lbs/in. and an elongation of 57%. When 0.5 part of cobalt chloride was used as the activator in the above recipe and 1 part of 2-mercapto-4-ethylthiazole was used as the modifier, a tensile strength of 3100 lbs/in. and an elongation of 510% was exhibited by the copolymer when it was tested in a tire tread recipe.

It is not necessary that the butadiene and the isoprene enter into the three-component copolymers in equal proportions, for a larger amount of either may be employed, somewhat better results ordinarily beingobtained when the amount of isoprene is not less than the amount oi butadiene. parts of butadiene, 80 parts of isoprene, 3 parts oi .acrylonitrile, 0.35 part of hydrogen peroxide, and 0.37 part oi sodium ferripyrophosphate were agitated at C. in about 250 cc. of a 5% aqueous solution of myristic acid which had been neutralized with sodium hydroxide. In 46 hours, 100 parts of synthetic rubber were formed which exhibited a tensile strength of 2600 1bs./in.'' and an elongation 02 420% when tested in a tire tread recipe.

Although I have herein disclosed specific embodiments 0! my invention, the invention is not to be limited solely thereto, for many modifications which will be apparent to those skilled in the art are within the spirit and scope of the invention as defined in the appended claims.

1. The method which comprises polymerizing in the form of an aqueous emulsion a mixture containing at least two butadiene-1,3 hydrocarbons and from about -2 to 10% by weight based on the butadiene hydrocarbons of an alpha.- methylene nitrile.

2. The method which comprises poLvmerizing in the form of an aqueous emulsion a mixture of butadiene, isoprene, and from about 2 to 10% by weight based on the butadiene and isoprene of acrylonitrile.

3. The method which comprises polymerizing in the form or an aqueous emulsion a mixture oi approximately equal proportions of butadiene and isoprene, and from about 2 to 10% by-weight based on the butadiene and isoprene of acrylonitrile.

4. The method which comprises polymerizing in the form of an aqueous emulsion a mixture of butadiene, isoprene, and from about 2 to 10% by weight based on the butadiene and isoprene o! acrylonitrile, said polymerization being effected in the presence of from 5 to 15% by weight based on the butadiene and isoprene of a water-soluble soap derived from a fatty acid containing between 10 and 20 carbon atoms per molecule.

5. The method which comprises polymerizing in the form of an aqueous emulsion a mixture of butadiene, isoprene, and from about 2 to 10% by weight based on the butadlene and isoprene of acrylonitrile, said polymerization being eiiected in the presence of from 5 to 15% by weight based on the butadiene and isoprene of a watersoluble soap derived from a fatty acid containing between 10 and 20 carbon atoms per molecule and a small amount of a heavy metal catalyst.

63. The method which comprises polymerizing in the form of an aqueous emulsion a mixture of butadiene, isoprene, and from about 2 to 10% by weight based on the butadiene and isoprene of acrylonitrile, said polymerization being eiiected in the presence of from 5 to 15% by weight based on the butadiene and isoprene of a watersoluble soap derived from a fatty acid containing; between 10 and 20 carbon atoms per molecule and a small amount of a heavy metal catalyst.

7. The method which comprises polymerizing in the form oi an aqueous emulsion a mixture of approximately equal proportions of vbutadiene and isoprene, and about 3% based on the imtadiene and isoprene of acrylonitrile, said polymerization being efiected in the presence of from 5 to 15% based on the butadiene and isoprene 02 sodium myristate and a sodium ferri pyrophosphate catalyst.

3. A composition prepared by the method oi claim 1.

0. A composition prepared by the method of claim 2.

10. A composition prepared by the method of claim 4.

11. A composition prepared by the method 01. claim 5. I

12. A composition prepared by the method oi claim'd.

13. A composition prepared by the method 02 claim 7.

CHARLES F. FRYLING.

Patent 310. 2,58h,'5hh

CERTIFICATE OF coRREcTI oN.

. S eptember '11, 191 .5. CHARLES FRYLING.

It is hereby certified, that error appears in th elprinted specification of the above niambered patent requiring correction as follows: Page 2, first solumn, linej for "57%" read 57075"; and that 'thesid Letters Patent should. be r ed -r.'&1;'Li-.h this correction therein that the same is; conform to the record 0f the case in the .Patnt Offic Signed and sealed this 19th day ofFebruary, A. 1).. 19%.

Leslie Frazet -(Seal) I First Assistant Commissioner of Patents. 

